Hello all,

I just got my 3 year allotment of isotope standards from NIST. I have a
brand new Delta Plus EA-Conflo setup and I need to calibrate some internal
lab standards. I do not have any other inlet available on my system. Just
wanted to poll the group and get some feed back on the following -

1) What general guidelines for standard handling, storage, and usage can
you suggest? I have all of the ammonium sulfate standards for N
(-30.4,+0.4,+20.3, and +53.5) and the sucrose and PEF stds for C ( -10.47
and -31.77).

2) What do you find to be the most useful internal lab standards? Are
people calibrating daily with EA standards (acetanilide, etc.) for both %
and delta values, or using other compounds? What compounds or which
suppliers of compounds give the most uniform results for %C/N and deltaC/N?

3) I've seen the suggestion to leave my Conflo Std gases set to a 0 delta
value in the software and to do a calibration curve external of the
software using my standards. This seems like a good idea and also seems
easy enough. Any comments/warnings about this?

4) I will be having to deal with enriched N samples at varying levels. Does
anyone have a good source for enriched standards that work well by EA?

Thanks,

Howard

Howard Sanford
919-513-3039
North Carolina State University
Dept. of Soil Science
Box 7619
3114 Williams Hall
Raleigh, NC 27695